eclipse 定义一个二维向量<a,b>类，其中a、b为其属性，主要操作如下： 向量相加：<a,b>+<c,d>=<a+c,b+d> 向量相减：<a,b>-<c,d>=<a-c,b-d> 向量内积：<a,b>*<c,d>=a*c+b*d 编程定义该类，并使用该类

以下是一个简单的实现示例：

public class Vector2D {
    private double x;
    private double y;

    public Vector2D(double x, double y) {
        this.x = x;
        this.y = y;
    }

    public Vector2D add(Vector2D other) {
        double newX = this.x + other.x;
        double newY = this.y + other.y;
        return new Vector2D(newX, newY);
    }

    public Vector2D subtract(Vector2D other) {
        double newX = this.x - other.x;
        double newY = this.y - other.y;
        return new Vector2D(newX, newY);
    }

    public double dotProduct(Vector2D other) {
        return this.x * other.x + this.y * other.y;
    }

    public double getX() {
        return x;
    }

    public void setX(double x) {
        this.x = x;
    }

    public double getY() {
        return y;
    }

    public void setY(double y) {
        this.y = y;
    }

    @Override
    public String toString() {
        return "<" + x + ", " + y + ">";
    }
}

我们可以使用以下代码进行测试：

Vector2D v1 = new Vector2D(1, 2);
Vector2D v2 = new Vector2D(3, 4);

System.out.println("v1 = " + v1);
System.out.println("v2 = " + v2);

Vector2D v3 = v1.add(v2);
System.out.println("v1 + v2 = " + v3);

Vector2D v4 = v1.subtract(v2);
System.out.println("v1 - v2 = " + v4);

double dotProduct = v1.dotProduct(v2);
System.out.println("v1 * v2 = " + dotProduct);

输出结果将是：

v1 = <1.0, 2.0>
v2 = <3.0, 4.0>
v1 + v2 = <4.0, 6.0>
v1 - v2 = <-2.0, -2.0>
v1 * v2 = 11.0